Embodiments of the present invention disclosed herein relate to a relaxation oscillator, and more particularly, to a relaxation oscillator for compensating for system delay.
Oscillator circuits are commonly used in many diverse electronic fields. A resistor-capacitor (RC) oscillation circuit generally includes a control circuit coupled to a connector positioned between serial RC networks. In order to generate an oscillation signal, the control circuit alternately charges or discharges a voltage applied to a capacitor through a resistor. An oscillation frequency is determined by the time constant of the resistor-capacitor circuit configuration.
One method of forming an RC oscillator employs the well-known NE 555 timer manufactured by National Semiconductor Corporation, as a circuit that controls charging and discharging of a capacitor of an RC network. The NE 555 timer includes a set/reset (SR) flip-flop and first and second comparators. A connector positioned between serial RC networks is coupled to one input terminal of each comparator. The other input terminal of the first comparator is coupled to receive a high threshold voltage (Vh), while the other input terminal of the second comparator is coupled to receive a low threshold voltage (Vl). An output terminal of the first comparator is coupled to a set input of a flip-flop, while an output terminal of the second comparator is coupled to a reset input of the flip-flop. An output terminal of the flip-flop is coupled to the resistor of the RC network.
With respect to operation, when the first comparator sets the flip-flop and an RC oscillation signal exceeds a predetermined high threshold voltage, discharging of the voltage is initiated through the capacitor, and when the second comparator resets the flip-flop and the RC oscillation signal drops below a predetermined low threshold voltage, charging of the voltage of the capacitor is initiated. A signal generated in a capacitor through the above method oscillates between a high threshold voltage and a low threshold voltage, with the oscillation frequency determined by values of the resistor and capacitor of the RC network.